Hydraulic digging machines

ABSTRACT

A hydraulic digging machine has a boom and a digging arm with a bucket. A first hydraulic power means is employed for normal operation of the digging arm. A second hydraulic power means is adapted to be connected to the digging arm when desired to assist the first hydraulic power means.

United States Patent [72] lnventor Hans Egron Karlsson Sater, Sweden[21] Appl. No. 761,655

[22] Filed Sept. 23, 1968 [45] Patented June 1, 1971 [73] AssigneeTeredo Maskin A.B.

Stockholm, Sweden [54] HYDRAULIC DIGGING MACHINES 3 Claims, 2 DrawingFigs.

[52] US. Cl

[51] 1nt.Cl

[50] Field of Search {56] References Cited UNITED STATES PATENTS3,073,465 1/1963 Strnad 3,094,229 6/1963 Johnson et a1,

3,239,083 3/1966 Guinot Primary ExaminerGera1d M. Forlenza AssistantExaminer-Frank E. Werner AlturneyCushman, Darby & Cushman ABSTRACT: Ahydraulic digging machine has a boom and a digging arm with a bucket. Afirst hydraulic power means is employed for normal operation of thedigging arm. A second hydraulic power means is adapted to be connectedto the digging arm when desired to assist the first hydraulic powerPATENTED JUN 1 IBYI SHEET 1 BF 2 fol INVENTOR. q karlssau HYDRAULICDIGGING MACHINES The present invention relates to hydraulic diggingmachines having a boom, a digging arm pivotally at the outer end of theboom and supporting a bucket for digging when the digging arm is swungby means of a hydraulic power means.

Hydraulic digging machines are becoming more used than digging machinescontrolled by means of a wire system. The reason for this is mainly thatthe boom, digging arm and bucket of the hydraulic digging machines maybe operated at a higher speed by means of hydraulic piston and cylinderassemblies. This is particularly true for digging machines of thesmaller sizes. However, when the volume of the bucket is increased togreater values, certain difficulties may arise when the resistance intheground or soil is high. To overcome this resistance it would bepossible to increase the size of the hydraulic cylinder actuating thedigging arm. However, such an increased size would require acorrespondingly stronger boom and a greater pump capacity, that is agreater power output from the engine of the machine. Therefore, adisadvantage of the hydraulic digging machines is that they are hithertonot quite as efficient for digging in hard soil and the like withbuckets having a relatively great volume, as so-called wire machines.

The general object of the invention is therefore to provide a hydraulicdigging machine which in a simple manner overcomes the above-mentioneddisadvantage.

To this end the hydraulic digging machine according to the invention ischaracterized by a second hydraulic power means provided toalternatively actuate the digging arm when an additional force isdesired to assist the first hydraulic power means connected to thedigging arm. ln a preferred embodiment of the invention the twohydraulic power means are controlled by a valve which in a first orneutral position admits pressure fluid merely to the first power meansand in a second or effective position admits pressure fluid to bothpower means. It is preferred that the second hydraulic power means isconnectedto the digging arm through a wire which may easily bedisconnected from the digging arm when not in use. The first hydraulicpower means is a hydraulic piston and cylinder assembly, and the secondhydraulic power means may be a hydraulic piston and cylinder assembly oralternatively a pressure fluid rotary motor driving a winch for pullingthe wire.

Further details and advantages of the invention will be disclosed morein detail with reference to the accompanying drawing wherein,

FIG. 1 illustrates a diagrammatic view showing the present invention andits associative hydraulic circuitry,

FIG. 2, illustrates a detail schematic view of a portion of thehydraulic circuitry of the present invention.

In FIG. 1 there is diagrammatically shown a digging assembly comprisinga boom 10, a digging arm 11, a bucket 12 and a pressure fluid system forcontrolling the hydraulic power means in the form of hydraulic pistonand cylinder assemblies, hereinafter referred to as cylinders.

The frame structure 13 supporting the boom may be carried on endlessbelts 14 or wheels in a conventional manner.

The boom, digging arm and bucket are in a known manner pivotally mountedand actuated by cylinders 15, 16 and 17 which are double acting asindicated by a pair of pressure fluid conduits 15a, 15b, 16a, 16b and17a, 17b to the respective cylinder.

From an oil reservoir 18 three pumps 15c, 16c and 170 feed pressure oilthrough valves 19, 20 and 21 to the cylinders 15, 16 and 17,respectively. Each pump-has a pressure conduit 22, 23 and 24,respectively, to its valve, and an oil return conduit 25, 26 and 27,respectively, from the valve to the reservoir 18. Between the valve 19and the reservoir 18 is an adjustable restriction or nozzle 25a toadjustably increase the flow resistance in conduit 25 for reasons givenhereinafter.

All valves 19, 20 and 21 may be moved from an intermediate neutralposition shown to either of two end positions. For example, when valve20 is shifted to its right-hand end position, pressure oil is admittedto conduit 16b, whereas oil leaves through conduit 16a and conduit 26 tothe reservoir 18. The digging arm is then swung inwards. Vice versa,when the valve 20 is in its left-hand end position, pressure oil isadmitted to conduit 16a, whereas conduit 16b is connected to the returnconduit 26. In the neutral position of valve 20, oil in conduit 26 isrecirculated directly through conduit 26.

The aforementioned parts of the machine are known per se and, therefore,have not been described in detail.

In accordance with the invention, the digging arm 11 may bealternatively actuated by a second hydraulic power means to assist thecylinder 16 when desired. To this end an additional cylinder 28 ismounted on the boom close to its inner end and has its piston rod 29connected to one end of a wire 30 running over two pulleys 31 and 32rotatably mounted on the boom. The other end of the wire is detachablysecured to an attachment 33 on the digging arm. A similar attachment 34is provided at the lower end of the digging arm 11, and further, thereis a similar attachment 35 on the boom near its outer end. Theattachments 33, 34, 35 are in the form of a pair of lugs with coaxialholes for a pin 36 which when inserted through the lugs and a hole inthe end piece 37 of the wire will secure the wire. Accordingly, the wiremay be rapidly shifted to any of the attachments 33, 34 and 35.

The cylinder 28 receives oil through a single conduit 38 because thecylinder is used merely for effecting a pull of the wire 30 whendesired. The supply or return of oil from the cylinder 28 throughconduit 38 is controlled by a valve 39 which may take two positions.

From conduit 16b there is a branch conduit 40 to the valve 39, but inthe shown position of valve 39 the conduit 40 is closed from conduit 38.Instead, conduit 38 is through the valve 39connected to a return conduit41 which in turn is connected to the return conduit 25 at a pointbetween the valve 19 and the restriction 25a which provides apredetermined, raised oil pressure in theconduits 41 and 38 when thecylinder 28 is idling, that is not used for effecting additional power.Alternatively, the restriction may be obtained by selecting a dimensionof the conduit 25 which will result in the same or desired resistance toflow as the restriction 250.

Due to the somewhat raised pressure in the conduit 41 as describedabove, this pressure will act on the piston in the cylinder 28 in orderto prevent slackening of the wire when the digging arm is swung undernormal operation, that is when no additional force is needed.

When additional force on the digging arm 11 is needed, the valve 39 isshifted to its second position in which conduits 38 and 40 are connectedand conduit 41 is closed from conduit 38. Accordingly, the pressure oilin conduit 16b will also be led to the cylinder 28. If the resistance todigging is extremely high in the ground, the wire 30 is attached to thelowermost attachment 34, which will result in the greatest lever arm tothe pivot 42 of the digging arm 11.

No extra pump is needed since the pump 16c for the operation of thenormal cylinder 16 is also employed to feed the cylinder 28. Of course,this means that the piston in the cylinder 16 will receive a less oilvolume per minute so that its speed is decreased. However, this is nodisadvantage under the circumstances when the bucket 12 .is meeting ahigh resistance to digging in the ground, particularly when this isfrozen.

The valve 39 may be shifted manually but it is preferably automaticallyshifted in response to the pressure in the conduit 16b. This may beobtained by means of any well known device for such purpose such as thatshown in FIG. 2. In this figure there is shown a separate branch conduit43 from conduit 16b to an oil pressure responsive device 45. Thisdevicemay comprise a microswitch operated by a spring biassed pressuremember connected to conduit 43 and closing the contacts of the switchwhen the pressure in conduits 16b, 43 exceeds a predetermined valuewhich corresponds to a relatively high load on the bucket and diggingarm. When the microswitch closes, electrical current will be admitted toan electromagnetic device which actuates the valve to shift it to itssecond position in which pressure oil is admitted to conduit 38. Whenthe pressure is again decreased below said predetermined value and asecond lower value in a known manner, the microswitch is disengaged andthe valve 39 returns to its neutral position. Thus, the additionalcylinder 28 will be used only when needed, and the digging arm will beswung at its normal speed to and from the position where the diggingresistance is high.

If the digging conditions are such that no additional force will berequired, the wire 30 is attached to the attachment on the boom.

lclaim:

I. In a hydraulic digging machine for loading, carrying and unloadingsoil and other materials having a boom, a digging arm pivotally mountedat the outer end of said boom and supporting a bucket for loading,carrying and unloading said soil, a first hydraulic power means forproviding a first actuation force on said digging arm to swing saiddigging arm against the resistance of said soil during loading, saidfirst hydraulic power means including a hydraulic piston and cylinderassembly, the improvement comprising:

a second hydraulic power means for selectively providing a second forceto assist said first hydraulic power in swinging said digging arm toovercome the resistance of said soil during loading, said secondhydraulic power means including a rotary hydraulic motor for driving awinch, said winch having a wire attached thereto and detachablyconnected to said digging arm for assisting said first hydraulic powermeans.

2. A machine according to claim 1, in which said first hydraulic powermeans is connected via a conduit connected to a pressure fluid pump,said conduit having a branch conduit connected to said second hydraulicpower means through a valve, which in a first and effective positionadmits pressure fluid to said second hydraulic power means, and in asecond and neutral position closes the supply of pressure fluid to saidsecond hydraulic power means and connects the same to a return conduitleading to an oil reservoir for said pump, said pump being connectablewith the first hydraulic power means through a control valve whichpermits fluid to return to said reservoir through said return conduitwhich includes an adjustable restriction to provide a desired raisedpressure in the return conduit, and said return conduit from said secondhydraulic power means is connected to said return conduit which includesthe restriction and has said raised pressure, said valve in said branchconduit leading to said second hydraulic power means being automaticallycontrolled by a fluid pressure responsive device adapted to shift saidvalve to its effective position when a predetermined fluid pressure isexceeded in the pressure fluid conduit to said first hydraulic powermeans and to shift said valve back to its neutral position when saidfluid pressure is thereafter decreased below a predetermined value.

3. A machine according to claim 2, in which said fluid pressureresponsive device includes an electromagnetic power device adapted tomove said valve between its neutral and effective positions, and theelectric current to the electromagnetic device is controlled by amicroswitch adapted to be closed by a pressure responsive deviceinfluenced by the pressure fluid in said conduit to said first hydraulicpower means.

1. In a hydraulic digging machine for loading, carrying and unloadingsoil and other materials having a boom, a digging arm pivotally mountedat the outer end of said boom and supporting a bucket for loading,carrying and unloading said soil, a first hydraulic power means forproviding a first actuation force on said digging arm to swing saiddigging arm against the resistance of said soil during loading, saidfirst hydraulic power means including a hydraulic piston and cylinderassembly, the improvement comprising: a second hydraulic power means forselectively providing a second force to assist said first hydraulicpower in swinging said digging arm to overcome the resistance of saidsoil during loading, said second hydraulic power means including arotary hydraulic motor for driving a winch, said winch having a wireattached thereto and detachably connected to said digging arm forassisting said first hydraulic power means.
 2. A machine according toclaim 1, in which said first hydraulic power means is connected via aconduit connected to a pressure fluid pump, said conduit having a branchconduit connected to said second hydraulic power means through a valve,which in a first and effective position admits pressure fluid to saidsecond hydraulic power means, and in a second and neutral positioncloses the supply of pressure fluid to said second hydraulic power meansand connects the same to a return conduit leading to an oil reservoirfor said pump, said pump being connectable with the first hydraulicpower means through a control valve which permits fluid to return tosaid reservoir through said return conduit which includes an adjustablerestriction to provide a desired raised pressure in the return conduit,and said return conduit from said second hydraulic power means isconnected to said return conduit which includes the restriction and hassaid raised pressure, said valve in said branch conduit leading to saidsecond hydraulic power means being automatically controlled by a fluidpressure responsive device adapted to shift said valve to its effectiveposition when a prEdetermined fluid pressure is exceeded in the pressurefluid conduit to said first hydraulic power means and to shift saidvalve back to its neutral position when said fluid pressure isthereafter decreased below a predetermined value.
 3. A machine accordingto claim 2, in which said fluid pressure responsive device includes anelectromagnetic power device adapted to move said valve between itsneutral and effective positions, and the electric current to theelectromagnetic device is controlled by a microswitch adapted to beclosed by a pressure responsive device influenced by the pressure fluidin said conduit to said first hydraulic power means.